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Killer hornets, also known as Asian giant hornets (Vespa mandarinia), are the largest wasps in the world. These hornets are naturally present in Asia, but humans have accidentally introduced them to North America where they pose a threat to native wildlife as they kill other insects, including little wasps and bees.
The name “murderous hornet” is widely used online, but it can be sensational, according to the Natural History Museum in London. These hornets do not actively hunt humans, but they can kill humans with powerful stings if they feel threatened, especially when people are allergic to their venom.
What do murderous hornets look like?
Killer hornets are up to 2 inches (5.1 centimeters) long, about the length of a human inch. They have a yellow or orange head that contrasts with their predominantly dark brown or black thorax – the middle part of their body between the head and abdomen. Their large abdomens have alternating stripes of dark brown or black and yellow or orange, according to the United States Department of Agriculture (USDA). Killer hornets have large stingers about 6 millimeters long.
Related: Here’s how to distinguish a “deadly hornet” from other nasty wasps
What do murderous hornets eat?
Killer hornets are omnivorous and eat a range of insects, especially beetles, as well as sap and fruit, according to Animal Diversity Web (ADW) at the University of Michigan. Hornets often hunt alone, but they are best known for their coordinated “slaughter” attacks on beehives, where several hornets launch a full assault on a much smaller colony of bees. During these attacks, up to 20 or more hornets use their mandibles to tear apart the bees guarding the hive, then infiltrate and destroy the rest of the colony.
Killer hornets can kill around 30,000 individuals in a bee colony in a “slaughter” attack. After most of the adult bees are dead, hornets concentrate on bee larvae and pupae – the dormant form of bees between larvae and adults. According to the University of Florida, murderous hornets steal the larvae and pupae of bees and return them to their nests to feed on their own larvae.
Highlights
Cut: Up to 2 inches (5.1 centimeters) long
Lifetime: Up to a year (queens)
Conservation state: Not listed
Bee stings cannot penetrate the thick outer skin of hornets, but Japanese bees (Apis cerana japonica) have a strategy to defend their colonies against these devastating hornet attacks. The bees in unison swarm an invading hornet and trap it in a tight ball of their combined bodies. They then vibrate their bodies together to heat the ball until it reaches around 116 degrees Fahrenheit (47 degrees Celsius), which is hot enough to kill the hornet inside but not too hot to kill the bees. , Live Science reported previously. Bees living outside the killer hornet’s natural range, such as the native yellow bumblebees of North America (Hot bumblebee) and European bees (Apis mellifera) – which are not native to North America but contribute to the pollination of crops, have not evolved alongside the fierce giant hornets, and have no strategies to defend against attacks from deadly hornets. This makes the invading hornets more of a threat to them.
How did the murderous hornets get to the United States?
Scientists don’t know how the deadly hornets got to North America, but pest control guidelines released by the USDA’s Animal and Plant Health Inspection Service suggest it could be due to the intentional or unintentional illegal importation of live hornets. Killer hornets are eaten all over Asia for food and used in traditional medicines, and their nests, containing larvae and pupae, are harvested and sold, so it is possible that some live larvae and pupae were imported and escaped. Another possible route to North America is to kill hornets that accidentally get stowed away in international freight. Researchers believe that a similar species called Asian hornets or yellow-legged hornets (Vespa velutina), was accidentally introduced to France when a mated queen entered an international shipment, so this is another possible introduction scenario.
Killer hornets were first sighted in North America on Vancouver Island in Canada in August 2019. The hornets were then confirmed in the United States in December 2019, when the US Department of Agriculture Washington State (WSDA) verified two reports of hornets near Blaine, Washington, according to the WSDA. Eleven months later, entomologists located and destroyed Blaine’s first murderous hornet nest by attaching radio trackers to the live hornets they captured and following them to their nest, Live Science reported.
Other deadly hornets have been reported in Washington and Canada in 2020 and 2021. According to a statement released by the WSDA, a dead hornet found near Marysville, Washington, in June 2021 appeared to have no connection with any of the hornets previously discovered and therefore came from a separate introduction.
Related: Monstrous “murderous hornets” have reached the United States
Cycle of life
Killer hornets are social insects that live together in colonies or nests. All killer hornet colonies begin in the spring with a mated queen. Queens feed on tree sap as they search for a good place to start a colony – usually a cavity or hollow area near tree roots, according to the University of Florida. The queen creates comb cells by mixing her saliva with wood fibers and lays eggs in them, which then hatch as white larvae.
The queen feeds her larvae with tree sap, as well as insect and spider tissue that she gathers near the nest, until the larvae become pupae and then emerge as adults, according to Oregon State University. This process takes around 40 days. The queen initially produces only non-breeding worker hornets which take care of the maintenance of the colony, including nest enlargement and foraging, so that the queen can concentrate on laying eggs more and more of eggs.
Taxonomy of murderous hornets
Kingdom: Animalia
Phylum: Arthropods
To classify: Insect
Order: Hymenoptera
Family: Vespidae
Genus & Species: Vespa mandarinia
Source: NCBI
Breeding males and females, or queens, are born later in the year around the end of October. Males hang out near colony entrances to mate with new queens as they appear. Once a female has mated, she finds a place in the soil to overwinter and remains inactive until the next season, when she emerges and establishes a new colony, according to the University of Florida.
The queen of the original colony dies around mid-November and the colony fails shortly after without a queen to produce more workers. The queens of the murderous hornets live up to a year to give them enough time to establish and rule their colonies. Worker hornets only live from spring to winter, and male hornets live even less, typically dying after mating with a queen in the fall, according to ADW.
Related: Bees Beat ‘Killer Hornet’ Relatives with Poop
Are deadly hornets dangerous to humans?
According to the WSDA, murderous hornets can sting humans who attempt to pick them up, and will also sting when defending their nest or a hive that they attack. Their stings are more dangerous than native wasps and bees because they have longer stingers, deliver a greater dose of venom, and can sting repeatedly.
Killer hornets usually do not pose a threat to humans, but their stings can cause a serious allergic reaction, called anaphylaxis, in some people, similar to other stinging wasps, according to Oregon State University. Humans who suffer from a severe allergic reaction can be killed without treatment. In rare cases, a large number of deadly hornet bites can also lead to organ failure and death of people who are not allergic to the stings. According to a 2007 study published in the journal Clinical Toxicology, deadly hornets kill around 30 to 50 people each year in Japan.
The WSDA recommends that people be extremely careful if they are near deadly hornets, and people with allergies to bee or wasp stings should never approach them. If you come across a deadly hornet, you should stay calm and slowly leave the area or, if you are driving, slowly stop the car and open all the windows. If you encounter multiple hornets at once, the WSDA recommends running away or diving into dense brush for better protection against attack. A person should see a doctor promptly if they are stung several times and call emergency services if they are suffering from a severe or anaphylactic reaction, according to the Washington State Department of Health and the WSDA.
Additional resources
- The Washington State Department of Health website has more information on bee and wasp stings.
- National Geographic has a short YouTube video of Japanese bees defending themselves against a deadly hornet attack.
- The WSDA offers more information on deadly hornets in the United States and how to report a sighting.
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